1,720,982 research outputs found
A Separation Theorem for a Class of MIMO Discrete-Time Nonlinear Systems
No full textIn this paper the problem of output feedback stabilizability for a class of MIMO discrete-time nonlinear systems is considered. The proposed solution is based on an ad-hoc separation assumption that could be satisfied for the class of nonlinear systems characterized to have the full vector relative degree and the drift-observability properties. Numerical results for the simple academic case of pendulum show the effectiveness of this approach
The observer follower filter for stochastic differential systems with sample measurements
No full textSIMULTANEOUS DETERMINATION OF ATP, ITS METABOLITES AND NAD+ IN BLOOD BY HPLC WITH PHOTODIODE ARRAY DETECTOR
No full textSIMULTANEOUS DETERMINATION OF ATP, ITS METABOLITES AND NAD+ IN
BLOOD BY HPLC WITH PHOTODIODE ARRAY DETECTOR
Gueli Maria Concetta, Cusimano Vincenza, Lo Re Marianna, Giuseppe Salemi
Dipartimento di Biomedicina Sperimentale e Neuroscienze Cliniche (BioNEC), Università
degli Studi di Palermo.
Nucleotides are major high-energy phosphate carriers, subunits of nucleic acids and
precursors for the synthesis of nucleotide cofactors such as NAD+ and SAM. The study of
purine nucleotides metabolism is very important topic for a right understanding for the
cellular life. Living cells rely on ATP for growth, differentiation, and response to
physiological stimuli and environmental stress.
We propose a fast isocratic HPLC system with photodiode array detector (PDA) for the
simultaneous separation and quantification of major components of high-energy metabolism:
purine nucleotides (ATP, ADP, AMP), degradation products (nucleosides, bases)
simultaneously with NAD+ in human plasma in a single run.
Blood samples were obtained from the healthy adult volunteers (University workers/30). For
stability study, 200 mL of plasma was deproteinized through a Millipore-Amicon Ultracel.
Waters-HPLC system consisted of a 600E Pump; 2998 PDA; Empower TM2 DS; Atlantis T3
analitycal column (10μL loop). The m.f. was a 40 mmol/L potassium phosphate buffer, pH
2.2 with methanol 20% at a flow rate of 1.0 mL/min. The spectral range of the PDA was 200-
400 nm and the optimal wavelength was 254 nm.
We have obtained an execellent base-line separation of high-energy phospates, including
NAD+ as well as of their catabolic products. All the peaks were identified in order of elution:
ADP, ATP, adenine, AMP, hypoxantine, uric acid, xanthine, NAD+ , adenosine and inosine
(RT = 3.5; 3.6; 4.3; 5.4; 5.6; 6.3; 8.2; 10.2; 12.1; 19.1 min), respectively. Peaks were
identified by spiking the samples with authentic standards. This method makes use of a fastsingle-
step sample pre-treatment procedure and provides the assay of the key metabolites in
small amounts of plasma extracts. Therefore, this HPLC-PDA system is suitable to evaluate
the energetic state in a variety of cell types, both under normal and pathological events and is
very useful tool both in research and in clinical laboratories.
57° SIB FERRARA 18-19 Settembre 201
Pattern formation on a growing oblate spheroid. An application to adult sea urchin development
Get PDFIn this study, the formation of the adult sea urchin shape is rationalized
within the Turing's theory paradigm. The emergence of protrusions
from the expanding underlying surface is described through a reaction-diffusion
model with Gray-Scott kinetics on a growing oblate spheroid. The case of slow
exponential isotropic growth is considered. The model is first studied in terms
of the spatially homogenous equilibria and of the bifurcations involved. Turing
diffusion-driven instability is shown to occur and the impact of the slow
exponential growth on the resulting Turing regions adequately discussed. Numerical
investigations validate the theoretical results showing that the combination
between an inhibitor and an activator can result in a distribution of
spot concentrations that underlies the development of ambulacral tentacles in
the sea urchin's adult stage. Our findings pave the way for a model-driven experimentation
that could improve the current biological understanding of the gene control networks involved in patterning
Robust planar tracking via a virtual measurement approach
No full textIn thispapertheclassicalproblemofplanartrackingisstudied.Theapproachhereproposedisbasedon
the ideaofconsidering,assystemoutput,avectorof‘‘virtual’’measurementsdirectlyobtainedfromthe
actualones.Inthisway,themeasurementmapissplitintothesumofalineartime-varying
transformationofthestateandanuncorrelatedwhitenoiseprocess,whichisgenerallynongaussian.
The resultingmodelisamenableforapplyingstandardlinearandpolynomialKalmanlikealgorithms
avoidinganylinearizationprocedureofthemeasurementmap,whichisrequiredbyotherstandard
suboptimalsolutions(e.g.EKF).Finally,theproposedalgorithmsarecheckedthroughnumerical
simulation
Stochastic Modeling of Expression Kinetics Identifies Messenger Half-Lives and Reveals Sequential Waves of Co-ordinated Transcription and Decay
No full textThe transcriptome in a cell is finely regulated by a large number of molecular mechanisms able to control the balance between mRNA production and degradation. Recent experimental findings have evidenced that fine and specific regulation of degradation is needed for proper orchestration of a global cell response to environmental conditions. We developed a computational technique based on stochastic modeling, to infer condition-specific individual mRNA half-lives directly from gene expression time-courses. Predictions from our method were validated by experimentally measured mRNA decay rates during the intraerythrocytic developmental cycle of Plasmodium falciparum. We then applied our methodology to publicly available data on the reproductive and metabolic cycle of budding yeast. Strikingly, our analysis revealed, in all cases, the presence of periodic changes in decay rates of sequentially induced genes and co-ordination strategies between transcription and degradation, thus suggesting a general principle for the proper coordination of transcription and degradation machinery in response to internal and/or external stimuli
A carleman Discretization Approach to Filter Nonlinear Stochastic Systems with Sampled Measurements
No full textAn efficient approach to the design of observers for continuous-time systems with discrete-time measurements
No full textThis paper describes an efficient discretization approach for nonlinear continuous-time systems. A Carleman linearization approach is used to evaluate the exact coefficients of the Taylor-Lie expansion of the dynamics of the system. The resulting discretization scheme is used to build a discrete-time observer that displays good performance. The paper shows the advantages of using an integrated discretization - observation approach for large discretization interval
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